System and method for touch-to-display noise mitigation

ABSTRACT

Driving a display of an input-display device includes generating, during a first display frame, a first touch sensing waveform to be applied to a touch screen of the display, and generating, during a second display frame, a second touch sensing waveform to be applied to the touch screen. The first touch sensing waveform generates on the display a first touch-to-display noise pattern of touch-to-display noise artifacts. The second touch sensing waveform generates on the display a second touch-to-display noise pattern of touch-to-display noise artifacts. The second touch-to-display noise pattern mitigates the first touch-to-display noise pattern.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.17/525,846, filed on Nov. 12, 2021, which application is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The described embodiments relate generally to electronic devices, andmore specifically, to a technique for mitigating touch-to-display noisein a display system having a touch sensor screen.

BACKGROUND

Input devices including proximity sensor devices (e.g., touchpads ortouch sensor devices) are widely used in a variety of electronicsystems. Proximity sensor devices are often combined with displaydevices to operate as input-display devices (such as touch screensintegrated in cellular phones). In such an input-display device, theproximity sensor device and the display device may be highly integrated.The high integration may result in parasitic capacitances betweencomponents of the proximity sensor device and components of the displaydevice. As a result, a sensing waveform, emitted by the proximity sensordevice, may capacitively couple onto signals of the display device,thereby causing display artifacts.

Some displays, such as OLED displays, have significant coupling betweenthe touch sensor and the display, such that the touch sensor stimulationvoltages can couple into the display pixels and disrupt the intendedbrightness for a given display line. These artifacts have been termed“touch-to-display noise” that is defined as the display noise caused bytouch sensing.

SUMMARY

In general, in one aspect, one or more embodiments relate to aninput-display device. The input-display device includes a display screendisposed on a display substrate, the capacitive sensing electrodes forcapacitive sensing in a sensing region of the display screen, and adisplay controller module. The display screen includes display pixels.The display controller module includes a touch sensing controllerconfigured to generate, during a first display frame, a first touchsensing waveform to be applied to a touch screen of a display, andgenerate, during a second display frame, a second touch sensing waveformto be applied to the touch screen. The first touch sensing waveformgenerates on the display a first touch-to-display noise pattern oftouch-to-display noise artifacts, and the second touch sensing waveformgenerates on the display a second touch-to-display noise pattern oftouch-to-display noise artifacts. The touch-to-display noise patternmitigates the first touch-to-display noise pattern.

In general, in one aspect, one or more embodiments relate to a displaycontroller module. The display controller module includes a touchsensing controller configured to generate, during a first display frame,a first touch sensing waveform to be applied to a touch screen of adisplay, generate, during a second display frame, a second touch sensingwaveform to be applied to the touch screen. The first touch sensingwaveform generates on the display a first touch-to-display noise patternof touch-to-display noise artifacts. The second touch sensing waveformgenerates on the display a second touch-to-display noise pattern oftouch-to-display noise artifacts. The second touch-to-display noisepattern mitigates the first touch-to-display noise pattern.

In general, in one aspect, one or more embodiments relate to a methodfor driving a display of an input-display device. The method includesgenerating, during a first display frame, a first touch sensing waveformto be applied to a touch screen of the display, and generating, during asecond display frame, a second touch sensing waveform to be applied tothe touch screen. The first touch sensing waveform generates on thedisplay a first touch-to-display noise pattern of touch-to-display noiseartifacts. The second touch sensing waveform generates on the display asecond touch-to-display noise pattern of touch-to-display noiseartifacts. The second touch-to-display noise pattern mitigates the firsttouch-to-display noise pattern.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an input display device in accordance with one or moreembodiments.

FIG. 2 shows an input display device in accordance with one or moreembodiments.

FIG. 3 shows an input display device in accordance with one or moreembodiments.

FIG. 4 shows an example of touch-to-display noise in an input displaydevice.

FIG. 5 shows touch-to-display noise mitigation at high frequency inaccordance with one or more embodiments.

FIG. 6 shows touch-to-display noise mitigation at low frequency inaccordance with one or more embodiments.

FIG. 7 shows touch-to-display noise mitigation at low frequency inaccordance with one or more embodiments.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the disclosed technology or the application anduses of the disclosed technology. Furthermore, there is no intention tobe bound by any expressed or implied theory presented in the precedingtechnical field, background, or the following detailed description.

The present disclosure describes a system and a related method foravoiding the artifacts caused by touch-to-display noise using existingtouch controllers, such as, for example, OLED touch controllers.Touch-to-display noise is display noise that is caused by touch sensing.The disclosed system mitigates touch-to-display noise on input-displaydevices, including, for example, low-temperature polycrystalline oxide(LTPO) displays, using signals from display driver integrated circuit(DDIC) to the touch sensing controller integrated circuit.

The disclosed system distinguishes between high display refresh rates(60 Hz or greater) and low display refresh rates (below 60 Hz). For thehigh display refresh touch-to-display noise mitigation, the disclosedsystem cancels out the touch-to-display noise over multiple displayrefreshes. For the low display refresh, the disclosed system receivesinformation from the DDIC indicating the DDIC is about to transition toa low refresh rate mode. During the low refresh rate, the touch sensingoperation uses a touch-to-display noise avoidant sensing waveform forthe display refreshes that happen during low refresh rates. Once thedisplay is no longer updating, the touch sensing resumes normaloperations during the in-between time (i.e., the “Vbias” period of thedisplay) since the display is not vulnerable to touch-to-display noiseduring such periods.

Input-display devices, such as touchscreens, are widely used in avariety of electronic systems. Input-display devices may include asensing region, often demarked by a surface. In the sensing region, theinput-display device determines the presence, location, motion, and/orforce of one or more input objects. As used herein, touch sensingincludes proximity (e.g., no contact), touch (e.g., contact on an inputsurface), and contact with force. Touch sensing is implemented withtouch sensors. The touch sensors are electrodes that are used inperforming touch sensing. Examples of touch sensing includes mutual ortranscapacitive sensing and absolute or self-capacitive sensing. In oneor more embodiments, an input-display device includes a display screen.The display screen may be used to display content or information to auser, and the touch sensing may enable the user to interact with thedisplayed content. The touch sensing may involve driving the touchsensors with a sensing waveform, e.g., a square wave. The presence ofthe sensing waveform on the touch sensors may cause interference in thedisplay screen. The interference may result in display artifacts, suchas darker and/or lighter regions in the display screen, e.g., in astriped pattern. In one or more embodiments, the driving of the displayscreen is performed in a manner compensating for the interference, suchthat the artifacts are reduced or avoided.

FIG. 1 is a block diagram of an example of an input-display device(100), in accordance with one or more embodiments. The input-displaydevice (100) may be configured to provide input to an electronic system(not shown). As used in this document, the term “electronic system” (or“electronic device”) broadly refers to any system capable ofelectronically processing information. Some non-limiting examples ofelectronic systems include personal computers, such as desktopcomputers, laptop computers, netbook computers, tablets, web browsers,e-book readers, smart phones, personal digital assistants (PDAs),automotive infotainment devices, gaming devices, etc.

In FIG. 1 , the input-display device (100) includes a proximity and/orforce sensor device (e.g., “touchpad” or a “touch sensor device”)configured to sense input provided by one or more input objects (140) ina sensing region (120). Example input objects include styli, an activepen, and fingers.

The sensing region (120) encompasses any space above, around, in and/ornear the input-display device (100) in which the input device (100) isable to detect user input (e.g., user input provided by one or moreinput objects). The sizes, shapes, and locations of particular sensingregions may vary widely from embodiment to embodiment.

The input-display device (100) may utilize any combination of sensorcomponents and sensing technologies to detect user input in the sensingregion (120). The input-display device (100) includes one or moresensing elements for detecting user input. As a non-limiting example,the input-display device (100) may use capacitive techniques.

In some capacitive implementations of the input-display device (100),voltage or current is applied to create an electric field. Nearby inputobjects cause changes in the electric field and produce detectablechanges in capacitive coupling that may be detected as changes involtage, current, or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitance sensing elements to create electricfields. In some capacitive implementations, separate sensing elementsmay be ohmically shorted together to form larger sensor electrodes.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g., system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects. Thereference voltage may be a substantially constant voltage or a varyingvoltage and in various embodiments; the reference voltage may be systemground. Measurements acquired using absolute capacitance sensing methodsmay be referred to as absolute capacitance measurements.

Some capacitive implementations utilize “mutual capacitance” (or “transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a mutual capacitance sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes” or “transmitter”, TX) and oneor more receiver sensor electrodes (also “receiver electrodes” or“receiver”, RX). Transmitter sensor electrodes may be modulated relativeto a reference voltage (e.g., system ground) to transmit transmittersignals. Receiver sensor electrodes may be held substantially constantrelative to the reference voltage to facilitate receipt of resultingsignals. The reference voltage may be a substantially constant voltage.In various embodiments, the reference voltage may be system ground.

In some embodiments, transmitter sensor electrodes and receiver sensorelectrodes may both be modulated. The transmitter electrodes aremodulated relative to the receiver electrodes to transmit transmittersignals and to facilitate receipt of resulting signals. A resultingsignal may include effect(s) corresponding to one or more transmittersignals, and/or to one or more sources of environmental interference(e.g., other electromagnetic signals). The effect(s) may be thetransmitter signal, a change in the transmitter signal caused by one ormore input objects and/or environmental interference, or other sucheffects. Sensor electrodes may be dedicated transmitters or receivers ormay be configured to both transmit and receive. Measurements acquiredusing mutual capacitance sensing methods may be referred to as mutualcapacitance measurements.

The absolute capacitance measurements and/or the mutual capacitancemeasurements may be used to determine when at least one input object isin a sensing region, determine signal-to-noise ratio (SNR), determinepositional information of an input object, identify a gesture, determinean action to perform based on the gesture, a combination of gestures orother information, and/or perform other operations.

In FIG. 1 , a processing system (110) is shown as part of theinput-display device (100). The processing system (110) is configured tooperate the hardware of the input-display device (100) to detect inputin the sensing region (120). The processing system (110) includes partsof or all of one or more integrated circuits (ICs) and/or othercircuitry components. For example, a processing system may includecircuitry for mutual and/or absolute capacitance sensing. In someembodiments, the processing system (110) also includeselectronically-readable instructions, such as firmware code, softwarecode, and/or the like. In some embodiments, components composing theprocessing system (110) are located together, such as near sensingelement(s) of the input-display device (100). In other embodiments,components of processing system (110) are physically separate with oneor more components close to the sensing element(s) of the input-displaydevice (100), and one or more components elsewhere.

For example, the input-display device (100) may be a peripheral coupledto a computing device, and the processing system (110) may includesoftware configured to run on a central processing unit of the computingdevice and one or more ICs (perhaps with associated firmware) separatefrom the central processing unit. As another example, the input-displaydevice (100) may be physically integrated in a mobile device, and theprocessing system (110) may include circuits and firmware that are partof a main processor of the mobile device. In some embodiments, theprocessing system (110) is dedicated to implementing the input-displaydevice (100). In other embodiments, the processing system (110) alsoperforms other functions, such as driving haptic actuators, etc.

In some embodiments, the input-display device (100) includes a touchscreen interface, and the sensing region (120) overlaps at least part ofan active area of a display screen (155). For example, the input-displaydevice (100) may include substantially transparent sensor electrodesoverlaying the display screen and provide a touch screen interface forthe associated electronic system. The display screen may be any type ofdynamic display capable of displaying a visual interface to a user andmay include any type of light emitting diode (LED), organic LED (OLED),microLED, liquid crystal display (LCD), or other display technology. Theproximity and/or force sensor device and the display screen of theinput-display device (100) may share physical elements. For example,some embodiments may utilize some of the same electrical components fordisplaying and sensing. In various embodiments, one or more displayelectrodes of a display device may be configured for both displayupdating and input sensing. As another example, the display screen maybe operated in part or in total by the processing system (110).

While FIG. 1 shows a configuration of components, other configurationsmay be used without departing from the scope of the invention. Forexample, various components may be combined to create a singlecomponent. As another example, the functionality performed by a singlecomponent may be performed by two or more components.

FIG. 2 shows an input-display device (200) in accordance with one ormore embodiments. As shown in FIG. 2 , input-display device (200)comprises a display controller module (210) and a sensing-display module(220) that are coupled via routing traces (205). The sensing-displaymodule (220) may implement all or a part of the sensing region (120) andall or a part of the display screen (155), discussed above in referenceto FIG. 1 .

In a first embodiment, the display controller module (210) includes adiscreet display driver integrated circuit (DDIC) (250) and a discreettouch sensing controller integrated circuit (IC) (255). In a secondembodiment, the display controller module (210) may include a touch anddisplay driver integrated (TDDI) circuit that incorporates all of thefunctionality of the DDIC (25) and the touch sensing controller IC (225)in a single device. In the descriptions and claims that follow, the DDIC(250) may simply be referred to as “display driver 250” or “displaydriver”. Similarly, the touch sensing controller IC (255) may simple bereferred to as “touch sensing controller (255)” or “touch sensingcontroller”.

In one or more embodiments, the sensing-display module (220) includesmultiple layers, including a stack of display layers (230), one or morecapacitive sensing layers (232), and a display substrate (222). Thedisplay layers (230) form a display screen. In one embodiment, thedisplay screen is an OLED display. Accordingly, the stack of displaylayers (230) may include OLED display layers such as an organic emissivelayer, an anode layer, a cathode layer, one or more conductive layerswhich may include a thin-film transistor (TFT) layer, etc. The stack ofdisplay layers (230) may be disposed on the display substrate (222). Inone embodiment, the display substrate (222) is a flexible plasticsubstrate, to enable a flexible, rollable and/or foldable OLED display.

The stack of display layers (230) may include microLED layers such as alayer of LEDs disposed on a thin-film transistor (TFT) layer on thedisplay substrate (222). The stack of display layers (230) may includeLCD display layers such as a color filter glass layer, a liquid crystallayer, and a TFT layer disposed on the display substrate (222), whichmay be glass.

The sensing-display module (220) may have additional layers andcomponents. In one or more embodiments, multiple transmitter (TX)electrodes (234) and/or receiver (RX) electrodes (236) are disposed inthe one or more capacitive sensing layers (232) in a sensing region ofthe display screen. The sensing region may span all or part of thedisplay screen. The TX electrodes (234) and/or RX electrodes (236) maybe used in capacitance sensing (e.g., absolute capacitance sensing,mutual capacitance sensing, etc.), as described above in reference toFIG. 1 .

While FIG. 2 shows the capacitive sensing layer(s) (232) as beingdisposed on top of the stack of display layers (230), these layers maybe located anywhere, relative to the stack of display layers (230). Forexample, one layer with RX electrodes (236) may be located on top of thestack of display layers (230), and another layer with TX electrodes(234) may be located in or below the stack of display layers (230).Alternatively, there may be no layer with TX electrodes. In one or moreembodiments, the sensing module (220) includes a matrix pad sensor withnumerous sensing pads and traces connecting to the sensing pads in ametal mesh layer across the sensing region. The matrix pad sensor mayinclude at least one such metal mesh layer. Instead of using a dedicatedmetal mesh layer, a display layer (e.g., an OLED display cathode layer)may be patterned to serve as a metal mesh layer.

In one or more embodiments, the TX electrodes (234) and the RXelectrodes (236), together, implement mutual capacitance sensing. Inother words, a waveform is driven onto the TX electrodes (234) and aresulting signal(s) is received from the RX electrodes (236). Theresulting signal is a function of the waveform and change in capacitancebetween the TX electrodes (234) and RX electrodes (236) due to thepresence of an input object. In one or more embodiments, the RXelectrodes (236) are operated to perform absolute capacitance sensingindependent of the TX electrodes (234). In one or more embodiments, thetransmitter electrodes (234) are operated to perform absolutecapacitance sensing independent of the receiver electrodes (236).

In one or more embodiments, the stack of display layers (230) includesone or more layers (e.g., a thin-film transistor (TFT) layer) withsource lines and gate lines and transistors for controlling theindividual OLED, LCD or microLED units of the display pixels (or pixels)of the display screen. In one or more embodiments, one or more sourcelines and/or one or more gate lines are also operated to performabsolute capacitance sensing.

In one or more embodiments, the DDIC (250) includes a source drivercircuit (252) that drives the transistors controlling the pixels of thedisplay screen. Each of the pixels may include an OLED pixel, a microLEDpixel, a microOLED pixel, an LCD pixel, etc. The DDIC (250) may receivean image signal from a host application processor (e.g., a videoprocessor), or any other component (not shown) that provides imagecontent to be displayed on the display screen (155). The received imagesignal may be in digital form. The DDIC (250) may further include animage processing circuit (254) that may process the received imagesignal to output a processed image signal. For example, the imageprocessing circuit (254) may perform a mura correction and/or otherimage processing operations. The processed image signal may be providedto the source driver circuit (252) where an analog signal is generatedto drive the transistors associated with the pixels of the displayscreen, in accordance with one or more embodiments. The image processingcircuit (254) may be integrated in the DDIC (250) or the imageprocessing circuit (254) may be located elsewhere. Any kind ofadditional circuits related to the displaying of images may be includedin the DDIC (250), without departing from the disclosure.

In one or more embodiments, the touch sensing controller IC (255) isconfigured to perform capacitance sensing. The touch sensing controllerIC (255) may drive capacitive sensing electrodes (e.g., the TXelectrodes (234) or a subset of the TX electrodes (234)) and may receiveresulting signals from capacitive sensing electrodes (e.g., from the RXelectrodes (236) or a subset of the RX electrodes (236)), to determinethe presence and/or position of an input object (e.g., input object(140), discussed above in reference to FIG. 1 ). The touch sensingcontroller IC (255) may include various components. In one embodiment,the touch sensing controller IC (255) includes an analog frontend (256)configured to perform the capacitance sensing by driving the capacitivesensing electrodes, receiving the resulting signals, andanalog-to-digital converting the resulting signals. The digitalprocessing may be performed elsewhere, by a touch processing circuit(258), e.g., a microprocessor, digital signal processor, etc. In oneembodiment, the touch sensing controller IC (255) includes some or allelements of the touch processing circuit (258). Alternatively, the touchprocessing circuit (258) may be located elsewhere.

In one or more embodiments of the touch and display driver integrated(TDDI) circuit, the display controller module (210) may be housed in asingle semiconductor package (e.g., an application-specific integratedcircuit (ASIC)). The source driver circuit (252), the image processingcircuit (254), the analog frontend (256), and/or the touch processingcircuit (258) may be on separate dies or on a single die, in thesemiconductor package. The semiconductor package may be disposed on thedisplay substrate (222) or elsewhere. Further, embodiments of thedisclosure may include multiple TDDI circuits, each associated with adifferent region on the display of the sensing-display module (220).

FIG. 3 shows an input display device (300) in accordance with one ormore embodiments. The input-display device (300) comprises a displaypanel (320) driven by a display chip (310) that includes a displaydriver (250) and a touch panel (330), driven by a touch chip (350) thatincludes a touch sensing controller (255), as described above in FIG. 2. The touch sensing controller (255) in touch chip (350) provides atouch sensing waveform (360) for touch sensing. In one or moreembodiments, data about the touch sensing waveform (360) is shared withthe display driver (250) in display chip (310). In some embodiments ofthe input-display device (300), the touch sensing waveform (360) itselfmay be provided to the display chip (310). Accordingly, the displaydriver (250) in display chip (310) is aware of the timing, polarity, andamplitude of the touch sensing waveform (360) by receiving the touchsensing waveform (360). In some embodiments, the timing and polarityinformation may be provided by a pulse train transmitted using one ormore general purpose input/output (GPIO) pin(s) 340. The display driver(250) in display chip (310) also provides a horizontal sync (Hsync)signal and a vertical sync (Vsync) signal to the touch chip 350.

FIG. 4 shows an example of touch-to-display noise in an input displaydevice. In FIG. 4 , an unmitigated noise display driving (400) is shown.An exemplary data line (402) carries a data voltage (404) for driving apixel (e.g., a single OLED (406)). The data voltage (404) may be asquare wave signal originating from the source driver circuit (252) ofthe DDIC (250), described in reference to FIG. 2 .

Due to resistances and capacitances that are associated with the routingtrace carrying the data voltage (404) to the pixel circuit (408), thedata voltage (404) includes an onset transient. Upon activation of thegate line (410) of the pixel circuit (408), the data voltage (404) onthe data line (402) charges a capacitor, Cs_(t), to allow a currentthrough the OLED (406), based on the data voltage (404). Accordingly,the output of the OLED (406) may be governed by the data voltage (404),with a higher data voltage generally resulting in an increased lightoutput. The driving of an OLED, while illustrated for a single OLED, maybe performed for all OLEDs of a display screen. Variations of the pixelcircuits may be used, without departing from the disclosure. Further,other previously mentioned display technologies may be used, withoutdeparting from the disclosure.

In one or more embodiments, a touch sensing operation occurs, at leastin part, simultaneously with the driving of the display. As a result,the sensing waveform (412) may capacitively couple onto the data voltage(404) at the pixel circuit (408), via an interference pathway (414)(gray arrow). The sensing waveform (412) is similar to the touch sensingwaveform (360) in FIG. 3 . As illustrated, the sensing waveform (412)modulates the cathode potential (418), resulting in the cathodepotential waveform shown in FIG. 4 , based on the RC time constantassociated with, for example, R_(TRx) and C_(TRx). An interferencecapacitance, C_(interf), between the cathode layer of the display(display cathode (416)) and the data line (402) may further couple thesensing waveform (412) onto the data voltage (404), thereby resulting inthe deteriorated data voltage (420). The deteriorated data voltage (420)therefore includes an artifact on the data voltage (422) (e.g., avoltage fluctuation as illustrated in FIG. 4 ) caused by the sensingwaveform (412). The artifact (422) of the deteriorated data voltage(420) may cause a fluctuation in the output of the OLED (306).

In FIG. 4 , the example display output with artifacts (430) illustratespossible artifacts in the display output. In the example, the artifactsinclude a non-homogeneous display output comprising a touch-to-displaynoise pattern with rows of pixels that are lighter than normal and rowsof pixels that are darker than normal. Some rows of pixels are lighter,and some rows of pixels are darker, based on the capacitors, C_(st) ofthe OLEDs in the darker and lighter regions in the display output beingcharged to different voltages, as a result of the artifact (422) on thedeteriorated data voltage (420). While the described effect may occur inany type of sensing display module, the effect may be particularlynoticeable, and thus undesirable, in OLED-based sensing display modules(e.g., flexible, rollable and/or foldable OLED sensing display) moduleswhere the layers (as shown in FIG. 2 ) are highly integrated withminimal spacing, thus resulting in increased capacitive couplings (e.g.,C_(interf)) between conductive elements.

Further, the described effect may be particularly prominent when anabsolute capacitive sensing is employed because all capacitive sensingelectrodes involved in the absolute capacitive touch sensing may bemodulated with the same phase. However, the effect may also benoticeable in transcapacitive sensing configurations, where only some ofthe capacitive sensing electrodes may be modulated or where an oppositephase modulation may be used to reduce the effect. Similarly, the effectmay also be noticeable in hybrid sensing configurations which combine anabsolute capacitive sensing and a transcapacitive sensing.

FIG. 5 shows touch-to-display noise mitigation at high frequency displayrefresh rate in accordance with one or more embodiments. FIG. 5 showsselected signals associated with the displaying of an odd frame (510)and an even frame (520). In an exemplary embodiment, the odd frames(510) and the even frames (520) are generated at 120 Hz. In one or moreembodiments, the display driver (250) in the display chip 310 maygenerate timing signals such as a vertical sync (Vsync) signal,including Vsync pulse (531) and Vsync pulse (532), to start and/or enddisplay frames, such as odd frame (510) and even frame (520). In oneembodiment, the Vsync signal may additionally or alternatively identifyone or more vertical blanking periods within a display frame.

The Absolute Sensing signal in FIG. 5 is similar to the touch sensingwaveform (360) in FIG. 3 and the touch sensing waveform (412) in FIG. 4. The touch processing circuit (258) senses the falling edge of theVsync pulse (531) from the source driver circuit (252) and generates theAbsolute Sensing signal. Initially, a rising edge of the AbsoluteSensing signal occurs at rising pulse (541), which is followed insequence by a falling pulse (542), a rising pulse (543), and a fallingpulse (544), and other pulses. Optionally, the Absolute Sensing periodmay be followed by a transcapacitive sensing period. However, thesequence of pulses (541-544) may cause the example display output withartifacts (430) to occur, as shown in FIG. 4 . As a result, in the oddframe (510), the touch sensing waveform (360) creates a firsttouch-to-display noise pattern comprising rows of pixels that arelighter than normal and other rows of pixels that are darker thannormal.

However, according to the principles of the present disclosure, in theeven frame (520), the touch processing circuit (258) senses the fallingedge of the Vsync pulse (532) from the source driver circuit (252) andgenerates a one-half (½) sense cycle trigger delay (560) beforegenerating the Absolute Sensing signal, which includes a rising pulse(551), followed in sequence by a falling pulse (552), a rising pulse(553), and a falling pulse (554), and other pulses. The Absolute Sensingsignal in the even frame (520) is essentially a time-delayed version ofthe Absolute Sensing signal in the odd frame (510). The half sense cycletrigger delay effectively creates a phase-inverted Absolute Sensingsignal during the even frame (520). Thus, for example, the rising pulse(551) corresponds to the falling pulse (542) in the odd frame (510) andthe falling pulse (552) corresponds to the rising pulse (543) in the oddframe (510).

As a result of the phase-inverted Absolute Sensing signal, in the evenframe (520), the touch sensing waveform (360) creates a secondtouch-to-display noise pattern comprising rows of pixels that are darkerthan normal and other rows of pixels that are lighter than normal in thedisplay output with artifacts (430) in FIG. 4 . However, the secondtouch-to-display noise pattern in the even frame (520) is the inverse ofthe first touch-to-display noise pattern of dark rows of pixels andlight rows of pixels in the odd frame (510). Effectively, brighttouch-to-display noise artifacts in a first display refresh become darktouch-to-display noise artifacts in the second display refresh and darktouch-to-display noise artifacts in the first display refresh becomebright touch-to-display noise artifacts in the second display refresh.The switching of bright and dark artifacts nets out to zero effect onbrightness. Advantageously, because the refresh rate is 60 Hz or higher,the human eye cannot detect the switching of bright and dark artifacts.

FIG. 6 shows touch-to-display noise mitigation at low frequency refreshrate (i.e., less than 60 Hz) in accordance with one or more embodiments.In an exemplary embodiment, the odd frames and the even frames aregenerated at 10 Hz. In FIG. 6 , the display driver (250) may generatetiming signals such as vertical sync (Vsync) signals and horizontal sync(Hsync) signals to start and/or end display frames and to start and/orend scan lines. However, a new GPIO signal on GPIO pin (340) istransmitted from the display driver (255) in display chip (310) to thetouch controller chip (350) to indicate when display data is valid for alow display refresh rate. The GPIO signal is an active low signal, asshown by falling (or negative going) pulses (610A) and (610B).

The “Display Status” value in FIG. 6 includes “Normal” periods (615A),(615B), and (615C) during which the display rate is 120 Hz, and thedisplay driver (250) performs gate scanning of pixel circuits, such asgate line (410) in FIG. 4 . The “Display Status” value in FIG. 6 alsoincludes the Vbias periods (620A) and (620B) during which the displayrefresh rate is 10 Hz and the display driver (250) in display chip (310)does not perform gate scanning.

During a low frequency refresh rate, the display driver (250) in displaychip (310) asserts the GPIO signal low during a data refreshing period.The GPIO signal is a low refresh rate signal indicating that displaydata is valid for a low display refresh rate. When the touch sensingcontroller (255) in touch chip (350) detects that the GPIO signal isLow, the touch sensing controller (255) responds either by disablingtouch sensing entirely or by only performing trans-capacitive sensing.The “Touch Status” value in FIG. 6 includes periods (630A) and (630B)during which the touch sensing controller (255) in touch chip (350)disables touch sensing entirely or only performs trans-capacitivesensing. The “Touch Status” value in FIG. 6 also includes periods (635A)and (635B) during which the touch sensing controller generates AbsoluteSensing signals and transcapacitive sensing signals in response to theVsync signal as shown above in FIG. 5 . However, because periods (635A)and (635B) occur during the Vbias periods (620A) and (620B) during whichthe display driver 2350) does not perform gate scanning, the AbsoluteSensing signal does not cause the example display output with artifacts(430) shown in FIG. 4 to occur.

FIG. 7 shows touch-to-display noise mitigation at low frequency inaccordance with one or more embodiments. FIG. 7 and FIG. 6 are similarin almost all respects. Therefore, FIG. 7 is not explained in detail toavoid redundant description. The significant difference between FIG. 7and FIG. 6 is that, in FIG. 7 , the GPIO signal has been combined withthe Vsync signal to form a Vsync (New) signal. The Vsync (New) signalincludes a low signal level period 710A and a low signal level period710B. When the touch sensing controller (255) detects that the Vsync(New) signal is low, the touch sensing controller (255) responds as inFIG. 6 above—either by disabling touch sensing entirely or by onlyperforming trans-capacitive sensing during periods (630A) and (630B).

The disclosed system operates in different modes based on either a highdisplay refresh rate (i.e., 60 Hz or greater) or a low display refreshrate (i.e., less than 60 Hz). For high display refresh rates, thedisclosed system cancels out the touch-to-display noise over multipledisplay refreshes by switching the bright and dark artifacts betweenmultiple frames so that the changes in brightness have zero effect andthe switching is too fast to be detected by the human eye. For the lowdisplay refresh rates, the disclosed system receives information fromthe DDIC indicating the DDIC is about to enter a low display refreshrate period. During the low refresh rate period, the touch sensingcircuitry uses a touch-to-display noise avoidant sensing waveform forthe display refreshes that happen during low refresh rates. Once thedisplay is no longer updating, the touch sensing resumes normaloperations during the in-between time (i.e., the “Vbias” period of thedisplay) since the display is not vulnerable to touch-to-display noiseduring such periods.

Embodiments of the disclosure may be suitable for implementation using aTDDI architecture, combining the source driver circuit associated withthe displaying of images and the analog frontend associated with thetouch sensing. Embodiments of the disclosure may also be used where thesource driver circuit is separate from the analog frontend.

In the above detailed description of embodiments, numerous specificdetails are set forth to provide a more thorough understanding of thedisclosed technology. However, it will be apparent to one of ordinaryskill in the art that the disclosed technology may be practiced withoutthese specific details. In other instances, well-known features have notbeen described in detail to avoid unnecessarily complicating thedescription.

Throughout the application, ordinal numbers (e.g., first, second, third,etc.) may be used as an adjective for an element (i.e., any noun in theapplication). The use of ordinal numbers is not to imply or create anyparticular ordering of the elements nor to limit any element to beingonly a single element unless expressly disclosed, such as by the use ofthe terms “before”, “after”, “single”, and other such terminology.Rather, the use of ordinal numbers is to distinguish between theelements. By way of an example, a first element is distinct from asecond element, and the first element may encompass more than oneelement and succeed (or precede) the second element in an ordering ofelements.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theclaims.

What is claimed is:
 1. An input-display device, comprising: a displayscreen comprising a plurality of display pixels; a touch screencomprising a plurality of capacitive sensing electrodes in a sensingregion of the display screen; and a display and touch sensor controllerconfigured to: generate, during a first display frame, a first touchsensing waveform to be applied to the touch screen, wherein the firsttouch sensing waveform generates a first touch-to-display noise patternof touch-to-display noise artifacts; and generate, during a seconddisplay frame, a second touch sensing waveform to be applied to thetouch screen, wherein the second touch sensing waveform generates asecond touch-to-display noise pattern of touch-to-display noiseartifacts, wherein the second touch-to-display noise pattern mitigatesthe first touch-to-display noise pattern.
 2. The input-display device ofclaim 1, wherein the display and touch sensor controller is configuredto: generate, during a high frequency display refresh rate, a firstvertical sync signal during the first display frame and a secondvertical sync signal during the second display frame; generate the firsttouch sensing waveform in response to the first vertical sync signal;and generate the second touch sensing waveform in response to the secondvertical sync signal.
 3. The input-display device of claim 2, wherein:the first touch-to-display noise pattern comprises first brighttouch-to-display noise artifacts that are brighter than normal and firstdark touch-to-display noise artifacts that are darker than normal; andthe second touch-to-display noise pattern comprises second brighttouch-to-display noise artifacts that are brighter than normal andsecond dark touch-to-display noise artifacts that are darker thannormal, wherein the second touch-to-display noise pattern is an inverseof the first touch-to-display noise pattern.
 4. The input-display deviceof claim 3, wherein the first bright touch-to-display noise artifactscorrespond to the second dark touch-to-display noise artifacts and thefirst dark touch-to-display noise artifacts correspond to the secondbright touch-to-display noise artifacts.
 5. The input-display device ofclaim 4, wherein: the first touch-to-display noise pattern comprises afirst plurality of rows of pixels that are darker than normal and asecond plurality of rows of pixels that are brighter than normal; andthe second touch-to-display noise pattern comprises the second pluralityof rows of pixels that are darker than normal and the first plurality ofrows of pixels that are brighter than normal.
 6. The input-displaydevice of claim 1, wherein the second touch sensing waveform is atime-delayed version of the first touch sensing waveform.
 7. Theinput-display device of claim 1, wherein the display and touch sensorcontroller is further configured to: assert a low refresh rate signal;detect the low refresh rate signal; perform only trans-capacitivesensing when the low refresh rate signal is asserted; and performabsolute capacitive sensing and trans-capacitive sensing when the lowrefresh rate signal is unasserted.
 8. A display and touch controller,wherein the display and touch controller is configured to: generate,during a first display frame, a first touch sensing waveform to beapplied to a touch screen, wherein the first touch sensing waveformgenerates a first touch-to-display noise pattern of touch-to-displaynoise artifacts; and generate, during a second display frame, a secondtouch sensing waveform to be applied to the touch screen, wherein thesecond touch sensing waveform generates a second touch-to-display noisepattern of touch-to-display noise artifacts, wherein the secondtouch-to-display noise pattern mitigates the first touch-to-displaynoise pattern.
 9. The display and touch controller of claim 8, whereinthe display and touch controller is further configured to: generate,during a high frequency display refresh rate, a first vertical syncsignal during the first display frame and a second vertical sync signalduring the second display frame; generate the first touch sensingwaveform in response to the first vertical sync signal; and generate thesecond touch sensing waveform in response to the second vertical syncsignal.
 10. The display and touch controller of claim 9, wherein: thefirst touch-to-display noise pattern comprises first brighttouch-to-display noise artifacts that are brighter than normal and firstdark touch-to-display noise artifacts that are darker than normal; andthe second touch-to-display noise pattern comprises second brighttouch-to-display noise artifacts that are brighter than normal andsecond dark touch-to-display noise artifacts that are darker thannormal, wherein the second touch-to-display noise pattern is an inverseof the first touch-to-display noise pattern.
 11. The display and touchcontroller of claim 10, wherein the first bright touch-to-display noiseartifacts correspond to the second dark touch-to-display noise artifactsand the first dark touch-to-display noise artifacts correspond to thesecond bright touch-to-display noise artifacts.
 12. The display andtouch controller of claim 11, wherein: the first touch-to-display noisepattern comprises a first plurality of rows of pixels that are darkerthan normal and a second plurality of rows of pixels that are brighterthan normal; and the second touch-to-display noise pattern comprises thesecond plurality of rows of pixels that are darker than normal and thefirst plurality of rows of pixels that are brighter than normal.
 13. Thedisplay and touch controller of claim 8, wherein the second touchsensing waveform is a time-delayed version of the first touch sensingwaveform.
 14. The display and touch controller of claim 8, wherein thecontroller is further configured to assert a low refresh rate signal andto detect the low refresh rate signal and, in response, to: perform onlytrans-capacitive sensing when the low refresh rate signal is asserted;and perform absolute capacitive sensing and trans-capacitive sensingwhen the low refresh rate signal is unasserted.
 15. A method for drivinga display of an input-display device, the method comprising: generating,during a first display frame, a first touch sensing waveform to beapplied to a touch screen, wherein the first touch sensing waveformgenerates a first touch-to-display noise pattern of touch-to-displaynoise artifacts; and generating, during a second display frame, a secondtouch sensing waveform to be applied to the touch screen, wherein thesecond touch sensing waveform generates a second touch-to-display noisepattern of touch-to-display noise artifacts, wherein the secondtouch-to-display noise pattern mitigates the first touch-to-displaynoise pattern.
 16. The method of claim 15, further comprising:generating, during a high frequency display refresh rate, a firstvertical sync signal during the first display frame and a secondvertical sync signal during the second display frame, wherein the firsttouch sensing waveform is generated in response to the first verticalsync signal and the second touch sensing waveform is generated inresponse to the second vertical sync signal.
 17. The method of claim 16,wherein: the first touch-to-display noise pattern comprises first brighttouch-to-display noise artifacts that are brighter than normal and firstdark touch-to-display noise artifacts that are darker than normal; andthe second touch-to-display noise pattern comprises second brighttouch-to-display noise artifacts that are brighter than normal andsecond dark touch-to-display noise artifacts that are darker thannormal, wherein the second touch-to-display noise pattern is an inverseof the first touch-to-display noise pattern.
 18. The method of claim 17,wherein the first bright touch-to-display noise artifacts correspond tothe second dark touch-to-display noise artifacts and the first darktouch-to-display noise artifacts correspond to the second brighttouch-to-display noise artifacts.
 19. The method of claim 15, whereinthe second touch sensing waveform is a time-delayed version of the firsttouch sensing waveform.
 20. The method of claim 15, further comprising:asserting a low refresh rate signal; detecting the low refresh ratesignal and, in response: performing only trans-capacitive sensing whenthe low refresh rate signal is asserted; and perform absolute capacitivesensing and trans-capacitive sensing when the low refresh rate signal isunasserted.